1

ATSC 2000: Introduction to Meteorology

Zhien WangDavid Rahn Cory Demko

Know Each OtherBrendan BryantBrian HagerCarl R NowakowskiDeborah Anne GraulHeath G. BrownJon StarrMarleigh Kay CogginMatthew Scott SmithAmanda R. JohnsonElizabeth R. Barnes

Leslie N. DarnallMonica Rae ValdezRachel L. ReynoldsBartley James BroganBrett Noel WormanBrian Thomas DeschChad Eugene PlumbChristopher L. HarndenDaniel G. Barrone

2

Daniel L. LogsdonJared AmrineJeremy C. KleinhansKyle Robert LangfossMarc Andrew HafnerMichael Boniface Molony IIMikel K. HoopesRaymond M. GallegosScott Elton HeadrickAmy M. Suchor

Brooke Ann SweeneyCatherine L. BrewerChelsie R. FrenchHauva ManookinJennifer M. VarilekSummer D. JohnsonNatalie Denise WestPaige Michelle VaskoSarah Georgia GrenggTrulan Wright Eyre

Why university science class?“A university education should help students

develop their ability to think critically and objectively and provide educational experiences necessary to make informed decisions in the future as members of society. A fundamental knowledge of some basic concepts in physical, earth and biological sciences is necessary if we are to think clearly and make wise choices concerning such issues as land use, food, energy and mineral resources, pollution, and global climatic changes.”

3

Why meteorology? • Why did you sign up?

• Importance of Meteorology (weather and climate)– Society: From drought and famine to devastating floods, some of

the greatest challenges we face come in the form of natural disasters created by weather.

– Personal: Dealing with weather and climate is an inevitable part of our lives. Sometimes it is as small as deciding what to wear for the day or how to plan a vacation. But it can also have life-shattering consequences, especially for those who are victims of a hurricane or tornado.

4

– Challenges: The dynamic nature of the atmosphere seems to demand our attention and understanding more these days than ever before: greenhouse warming , ozone depletion in the stratosphere, hurricanes, ...

A satellite movie of Hurricane Katrina

About this course

• The course is intended to aid your own personal understanding and appreciation of our earth’s dynamic atmosphere.

• Class Syllabus

5

Chapter 1

The Earth and its Atmosphere

The importance of Atmosphere

• Our atmosphere is a delicate life-giving blanket of air that surrounds the fragile earth.

• How long can we survive without the following:– Food – Water – Air

• What will happen if the earth without a atmosphere?

6

Fig. 1-1, p. 2

Overview of the Earth’s AtmosphereThe hot Sun is the center our solar system

Where we live!

The earth is at an average distance from the sun of nearly 150 million kilometer (km) or 93 million miles (mi). Energy from the sun drive everything on the earth.

Fig. 1-2, p. 3

Satellite image of the Earth and its Atmosphere

What exist in the atmosphere?

The earth’s atmosphere is a thin, gaseous envelope comprised mostly of nitrogen and oxygen, with small amounts of other gases, such as water vapor and carbon dioxide, aerosol, and clouds.

7

Fig. 1, p. 4

Figure 1: An atom has neutrons and protons at its center ( or nucleus). Molecules are combinations of two or more atoms. The air we breathe is mainly molecular nitrogen (N2) and molecular oxygen (O2).

A Breath of Fresh Air

•The volume of an average size breath of air is about a liter. •Near sea level, there are roughly ten thousand million million million (1022) air molecules in a liter.

A breath of air ≈ 1022 molecules

In the entire atmosphere, there are

nearly 1044 molecules.

Table 1-1, p. 3

Permanent Gases:NitrogenOxygenArgonHelium

HydrogenXenon

Variable Gases:Water vapor

Carbon dioxideMethane

Nitrous oxideOzone

ParticlesChlorofluorocarbons

Composition of the Atmosphere Near the Earth’s Surface

8

Fig. 1-3, p. 5

Water VaporThe most important variable gas: the amount vary a lot:

•In warm, steamy, tropical locations– up to 4%•In colder arctic areas – a mere fraction of a percent.

Examples showing the existence of water vapor:

Why water vapor change so much?

Fig. 1-3, p. 5

Water VaporWater vapor is invisible, but become visible after forming clouds (liquid or solid water).

9

Sources:

Sinks:

CO2A natural component of the atmosphere.

Low concentration: ~0.037%

An important greenhouse gas.

Long-term observations indicate that CO2 concentration is increasing !!!

Good or bad ?

Why CO2 concentration is increasing?

10

Fig. 1-6, p. 7

Ozone: a low concentration variable gas

Ozone hole over Antarctic

Good and bad aspects of ozone:

Table 1, p. 13

11

The Early atmosphere?

• The earth’s first atmosphere (~4.6 billion year ago): likely hydrogen and helium as well as hydrogen compounds ( such as methane and ammonia)

• Other gases increase as gases outpoured from the hot interior– Known as outgassing.

Fig. 1-7, p. 7

Erupting Volcanoes

What come out of erupting volcanoes:Water vapor (~80%)CO2 (10%)N2 (~ a few percent)

The second atmosphere !

12

Evolving the current atmosphere:~78% N2 and ~21% O2

High N2

More Water vapor

Clouds and precipitation

CO2 decrease

Air is rich in N2

High O2

High energy rays break water vapor

H2O H2 +O2

Important variables1. Weight

Weight = mass × gravity• An object’s mass is the

quantity of matter in the object not change

• Gravity change by many factors

– Locations on the earth– Change with altitude on the

Earth – Change with the mass of the

other object: moon, sun, and earth

The weight of the atmosphere near seal level is ~ 1.2 kg/ m3.

13

2. Density• The density of air (or any substance) is determined by the

masses of atoms and molecules and the amount of space between them.

volumeMoleculesofNumberdensityNumber =

volumemassdensityMass =

• Or measured with number of molecules rather than the mass:

Mass density of the atmosphere nears sea level?

Number density of the atmosphere nears sea level?

3 Temperature• The temperature of air (or any

substance) is a measure of its average kinetic energy. Simply stated, Temperature is a measure of the average speed of the atoms and molecules, where higher temperatures correspond to faster average speeds.

Temperature ScalesKelvin scale (K): absolute zeroFahrenheit scale (°F):Celsius scale (°C):

°C= 5/9 (°F -32)

K= °C + 273.15

14

4. Pressureareaforcepressure=

Applications of using the pressure definition:

How to increase pressure?

How to decrease pressure?

Increase forceor

Decrease area

Increase areaor

Decrease force

Air Pressure Demo

Pump

Tube

Water

Observe what happen when we pump air out of tube:

15

areaforcepressure=

• Air molecules are in constant motion. On a mild spring day near surface, an air molecule will collide about 10 billion times each second with other air molecules.

• Each time an air molecule bounces against a person or other surfaces, it gives a tiny push (force).

Air Pressure

Units of Air pressureMillibar (mb)

Hectopascal (hpa)Inches of Mercury (Hg)

The standard values of atmosphere at the seal level

1013.25 mb1013.25 hpa29.92 in Hg

How much pressure are you under? Earth's atmosphere is pressing against each square inch of you with a force of ~ 1 kilogram per square centimeter (14.7 pounds per square inch). The force on 1,000 square centimeters (a little larger than a square foot) is about a ton!

Laramie: 780 mb or 11.32 pounds per square inch

Physical Behavior of the Atmosphere

The following generalizations describe important relationships between temperature, pressure, density and volume, that relate to the Earth's atmosphere.

(1)When temperature is held constant, the density of a gas is proportional to pressure, and volume is inversely proportional to pressure.

(2) If volume is kept constant, the pressure of a unit mass of gas is proportional to temperature.

(3) Holding pressure constant, causes the temperature of a gas to be proportional to volume, and inversely proportional to density.

16

The Gas Laws

These relationships can also be described mathematically by the Ideal Gas Law. Two equations that are commonly used to describe this law are:Pressure x Volume = Constant x Temperature

andPressure = Density x Constant x Temperature

Demo to verify the relationship 3: Holding pressure constant …

Hot Water

Balloon Empty bottle

Air pressure and density decrease with height !

Do you have any experience to show these trends ?

17

Laramie~ 780 mb

Commercial aircraft flight altitude~ 200 mb

Summit of Mt. Everest~300 mb

Layer of the atmosphere

How Temperature changes with height ?

According to the temperature structure, the atmosphere can be divided into the following layers:

ExosphereThermosphereMesosphereStratosphereTroposphere

This is the average temperature profile!

18

Fig. 1-10, p. 11

Troposphere• On average 0- 11 km.• Contains all of the weather.• Is kept well stirred by rising and descending air currents.• Average lapse rate ( at which the air temperature decrease with height) is 6.5 °C/km or 3.6 °F /1000ft .•Temperature inversion can occur in this layer•The height of tropopause varies with latitude and season

•Higher over equatorial regions and lower in polar regions•Higher in summer and lower in winter

Fig. 1-10, p. 11

Stratosphere• Temperature increase with height, but is still extreme cold.

• The inversion suppress the vertical motion– stratosphere is a stratified layer.

• High ozone concentration– play a major part in heating air in this layer.

• The maximum ozone is around 25 km.

• The ozone layer absorb most solar UV radiation.

Ozone

19

Mesosphere (middle sphere)• Air is very thin here.• Temperature decrease with here.

Thermosphere• Temperature increase with height.• Oxygen molecules (O2) absorb energetic solar rays warming the air.•Solar activities highly impact temperature here.

Exosphere• Light molecule (such as H2)

can escape the earth’s gravitational pull

Temperature Variation

Lapse rate relatively constantwith latitude and season

Def: temperature inversion = region of negative lapse

rate

Tropopause height

20

Layers according to composition

HomosphereNitrogen and oxygen are well mixed (~78% and ~21%)

HeterosphereHeavier atoms and molecules ( such as oxygen and nitrogen) tend to settle to the bottom of the layer, while light gases (such as hydrogen and helium) float to the top.

Layer in terms of electrical properties : IonosphereAn electrical field region within the upper atmosphere where fairly large concentration of ions and free electrons exist.Ions – atoms and molecules that lost (or gained) one or more electrons.

Fig. 1-12, p. 16

Day Night

The ionosphere is very important for radio communication.

Strongly impacted by the solar activity.

21

Remote Sensing

Weather and Climate• Weather – the conditions of atmosphere at any

particular time and place.• Climate represents the accumulation of daily and

seasonal weather events over a long period time(mean and extremes)

Weather Elements 1. Air temperature – the degree of hotness of the air 2. Air pressure – the force of the air above an area3. Humidity – a measure of the amount of water vapor in the air4. Clouds – a visible mass of tiny water droplets and/or ice

crystals that are above the earth’s surface5. Precipitation -- any form of water, either liquid or solid (rain or

snow), that falls from clouds researches the ground6. Visibility– the greatest distance one can see 7. Wind – the horizontal movement of air

22

QUESTION FOR THOUGHT:Which of the following statements relate more to

weather and which relate more to climate?

a. the summers here are warm and humidb. cumulus clouds presently cover the entire skyc. our lowest temperature last winter was -29°Cd. the air temperature outside is 22°Ce. December is our foggiest monthf. the highest temperature ever recorded in

Phoenixville, PA was 44°C on July 10, 1936.g. snow is falling at the rate of 5 cm per hourh. the average temperature for the month of January

in Chicago, IL is -3°C.

Meteorology – a brief History• Meteorology - the study of the atmosphere and it's

phenomena• First discussed by Aristotle, 340 B.C.

– wrote a book entitled Meteorologica - summarized meteorological knowledge to date

• 17th-18th centuries - meteorology came into being with the advent of met instrumentation such as thermometers and barometers

• 19th century - met observations were being made routinely - transmitted with the telegraph

23

Meteorology – a brief History• 1920's - Concept of airmasses and fronts was

formulated in by Norwegian meteorologists– They developed a theory for the evolution of mid-

latitude cyclones - still used today!!• After WWII - meteorological radars were

implemented• 1950's - computers ran first models of the

atmosphere• 1960's - first meteorological satellites were

launched (Tiros I )• 1990's - National Weather Service was

modernized • We are now able to observe meteorological

phenomena on most all spatial scales!!!

Satellite View of Weather

24

Fig. 1-14, p. 21

Weather Map

Low and highpressure centers.

Wind – the horizontal movement of air• Winds to blow clockwise and outward from the center of high and count clockwise and inward toward the center of low.• Air rise in low – form clouds• Air sink in high –clear sky for most of time

Fronts: across which there is a sharp change in temperature, humidity and wind direction.

• Cold front

• Warm front

• Station front

• Occluded front

Fig. 1-15, p. 21

25

Weather Symbols and the Station ModelAppendix B